Full-vectorial analysis of high-index-contrast coupled channel waveguides

Coupling of two identical channel waveguides separated by an air gap is analyzed. The coupled structure exhibits a strong refractive index contrast in both the transverse and longitudinal dimensions, which necessitates the use of a full-vectorial model. The 3D full-vectorial bidirectional method-of-lines beam propagation is utilized for this purpose. The effect of the transverse and longitudinal displacements on the modal reflectivity and modal transmissivity of the fundamental TE-like and TM-like modes is reported. Numerical results are presented for both the full-vectorial model and the approximate semivec-torial model. A significant difference between the predictions of these two models is seen.